Department of Chemical and Process Systems Engineering
Permanent URI for this collectionhttps://cris.hit.ac.zw/handle/123456789/8
Browse
4 results
Search Results
Item Preparation and Characterization of Polymer-Grafted Montmorillonite-Lignocellulose Nanocomposites by In Situ Intercalative Polymerization(Journal of Applied Chemistry, 2016-07-11) Bunhu, Tavengwa; Chaukura, Nhamo; Tichagwa, LilianLignocellulose-clay nanocomposites were synthesized using an in situ intercalative polymerization method at 60∘ C and a pressure of 1 atm. The ratio of the montmorillonite clay to the lignocellulose ranged from 1 : 9 to 1 : 1 (MMT clay to lignocelluloses, wt%). The adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). FTIR results showed that the polymers were covalently attached to the nanoclay and the lignocellulose in the nanocomposites. Both TEM and XRD analysis showed that the morphology of the materials ranged from phase-separated to intercalated nanocomposite adsorbents. Improved thermal stability, attributable to the presence of nanoclay, was observed for all the nanocomposites. The nanocomposite materials prepared can potentially be used as adsorbents for the removal of pollutants in water treatment and purification.Item Equilibrium and kinetic studies on the adsorption of humic acid onto cellulose and powdered activated carbon(Taylor & Francis, 2015-08-24) Tavengwaa, Nikita Tawanda; Chimuka, Luke; Tichagwa, LilianThe removal of humic acid (HA) from aqueous solution onto cellulose (CE) and powdered activated carbon (PAC) was investigated in a batch adsorption system as a function of pH, sorbent mass and contact time. The optimum conditions for HA uptake by CE were 2–3, 50 mg and 30 min, respectively. For PAC, they were 2, 50 mg and 30 min, respectively. PAC and CE sorbents were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The kinetic adsorption data was analysed on the basis of Lagergren pseudo-first-order, pseudo-second-order, Bangham and the interparticle diffusion models. The Lagergren pseudo-first-order fitted the kinetic data best. Experimental sorption data were fitted on different adsorption isotherm models, and it was established that the fitting followed the order: Langmuir > Freundlich > Temkin > Dubinin–Radushkevich (D–R). According to the Langmuir isotherm models, the maximum adsorption capacities of CE and PAC for HA were 89.3 and 30.4 mg g−1 , respectively.Item Synthesis and Characterisation of Ag and Nitrogen Doped Tio2 Nanoparticles Supported on A Chitosan-Pvae Nanofibre(International Journal of Advanced Research in Chemical Science (IJARCS), 2014-04-04) Ocwelwang, Atsile Rosy; Tichagwa, LilianIn this studythe sol gel synthesis method was employed for the preparation of nitrogen and silver-doped TiO2nanoparticles.This was followed by immobilising the prepared nanoparticles onto chitosan (Cs) and polyvinyl alcohol-co-ethylene (PVAE) polymer fibres using the process of electrospinning. This was done so as to secure the particles on the Cs/PVAE matrix to allow their use in applications such as water treatment. Characterisation was carried out to establish some physical properties of the prepared particles. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Energy-dispersive x-ray Spectroscopy (EDX) were used to analyze the size, morphology and composition of the nanomaterials. Fourier Transform Infrared (FTIR) spectroscopy was used to monitor reactions and for identification of functional groups while X-ray diffraction (XRD) analysis was carried out to determine the crystalline phases of the synthesized material. The crystallite size was calculated using the Scherrer equation and the thermal stability of the nanocomposites was determined using Thermogravimetric analysis(TGA).The XRD patterns showed that the undoped and doped samples consisted of mixed crystalline phases of anatase and rutile. The diameter of randomly selected nanoparticles was found to range from 6.4 nm to 21 nm while the size of the nanofibres was found to be in the range 234-270 nm. Nitrogen doped titania nanoparticles were the smallest in size.Item Synthesis of Oligomers of 12-Acryloyloxydodecanoic Acid via Reversible Addition Fragmentation Transfer (RAFT) Polymerisation(International Journal of Chemistry, 2009-08-05) Tichagwa, Lilian; Sanderson, Ron; Pasch, HaraldA long chain fatty acid carrying an acryloyl functionality, 12-acryloyloxydodecanoic acid (12-ADA), was prepared from 11-hydroxydodecanoic acid and acryloyl chloride and used as monomer in the synthesis of oligomers of 12-ADA via the RAFT controlled polymerisation process. Reversible Addition Fragmentation Transfer (RAFT) reagents were prepared and used to control the polymerisation process and produced an oligomeric product with few monomeric units instead of a high molecular weight polymer of 12-ADA. The transfer reagents were prepared from Grignar intermediates from a reaction of dithioacids with free radical initiators 2,2-azobisisobutyronitrile (AIBN) and 4,4-azobis(4-cyanopropanoic acid) (ACP). It was found that short-chain oligomers in the form of dimers and trimers characterized by Electrospray Mass Spectrometry, ESMS and Gel Permeation chromatography, GPC were the major products obtained when RAFT reagents had been used in the controlled polymerisation. As a control, polymerisation was carried out in the absence of RAFT reagents and high molecular-weight polymers were obtained. This confirmed the effectiveness of the prepared RAFT reagents as polymerisation controllers and provided a way for the synthesis of oligomers. Here, the preparation of oligomers of 12-ADA using AIBN-RAFT reagents is reported. The method is expected to provide one way of preparing oligomers of controlled chain length/molecular mass which also carry a carboxylic acid functional group at one end.